During the WW1 aerial bombarding was not precise because planes were not equipped with radar. In fact pilots had to solely depend on their sight. When they see what they believed to be the target they deployed bombs. Using this opportunity of human error Parisians at the time thought of saving their town. They built a fake Paris so that the pilots will bomb it instead of the actual one. It even had a faux Arc di Tromphe and Goud du Nord among the landmarks.